This hydration system comes in four sizes and with two 8-ounce bottles, but you can add as many of these bottles as you want to the belt. The bottle mounts are removable and their positions can be adjusted along the length of the belt, making it easier for you to position them so they don’t collide with your forearms while you run. The bottles snap in to a plastic holster rather than a pocket. They are extremely easy to remove and replace, and feel secure on the belt as you run.Profile-design.com